Preface

The question how expensive a credit or how high the effective interest on a deposit is often has no clear answer.
There is nominal interest, effective interest and additional expenses that help confuse the consumer. And that is
not amazing, because your money is big buisness.

So let me try to explain the circumstances as simply as possible.

1.) effective interest = yield = internal rate of returnWhen you borrow money from somebody you will pay interest. This interest will be the yield for your credit giver.
So the math is the same; only the terms are depending on the side where you are standing.
And in both cases, you calculate the internal rate of return. Stop - you may think - and what about all the interest
formulas, which one learned sometimes ago? If everthing is that easy, why do we have them?
The answer: the IRR-formula is not easy to calculate - if you don´t have a computer. In former days you where happy
to have "simple" and solvable formulas for the calculation of the yield.

2.) nominal interest is for financial mathematiciansYou as a consumer are not interested in this.